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Friday, 9 September 2016

Fine Tuning the Mostly Printed CNC

After the last meetup at RPL, I decided to try and reduce the backlash issue that I'd been getting, about 3-4mm on the central junction. I eventually traced it to a combination of a fault in my Mini Kossel's calibration data and an offset in the STLs that made things a bit loose on one end of the brackets. My solution was to print some PLA tires for the 608 bearings and make up the gap that was causing the backlash.

608ZZ bearing and PLA tire/washer

After installing the tires, the observable backlash is reduced to less than 1 mm, hopefully fixing the problem.

Bearings with tires installed on centre block

The STL for the tire is here, it takes about 1 gram of filament, and 5 minutes to print one at 0.2mm layer height with a 0.4mm nozzle. As for installing them, you need to apply even pressure across the entire rim or the part will snap, so I'd recommend printing a few extras. Overall, probably one of the simplest fixes to a problem I've made so far.